PLANT PROTECTIVE RESPONSE TO ENHANCED UV‐B RADIATION UNDER FIELD CONDITIONS: LEAF OPTICAL PROPERTIES and PHOTOSYNTHESIS

Abstract

Abstract— Plants of Vicia faba were grown in the field during early to midsummer while receiving two levels of supplemental UV‐B radiation. Light‐saturated photosynthesis and stomatal diffusive conductance of intact leaves did not show any indications of UV‐radiation damage. Supplemental UV treatment did cause increased concentrations of UV‐absorbing flavonoid pigments in leaf tissues and decreased epidermal transmittance of UV radiation. While epidermal transmittance was reduced 30% under the low‐UV treatment, the high‐UV treatment failed to elicit as large a change. However, total amounts of flavonoids in other leaf tissues did increase in response to the high‐UV treatment (up to 12% greater per unit leaf area than for control plants). This may have been a major factor protecting underlying photosynthetic tissues.